Medium temperature carbonization of coal



rial rich in dull coal from coal.

Patented Aug. 31, 1937 PATENT OFFICE MEDIUM TEMPERATURE CARBQNIZATION OF COAL Hans August Koppers, Bochum, 'Germany, assignor, by mcsne assignments, to Koppers Company, a corporation of Delaware No Drawing. Application March 28, 1934, Serial No. 717,811. In Germany March 29, 1933 i 1 Claim.

My invention relates to the so-called medium temperature carbonization of coal in coking chambers, for example in the known horizontal chamber ovens, in order to obtain a solid coke of large size which is comparatively rich in volatile constituents (8-12% volatile matter) and highly reactive. In the scope of this specification the term medium temperature carbonization means a carbonization in which the walls of the coking chamber are heated to a temperature of from 500 to 750, centigrade, preferably 680, and in which the coke cake is pushed as'soon as condensable hydrocarbons do not longer escape.

With the coking temperatures indicated it is not possible at all events, to produce a solid and large coke from all kinds of original coal. In particular, with original coal which in itself contains higher quantities of binder (bitumen) than it is required for binding the non-fusible constituents of the original coal, only a porous and brittle coke is produced by the medium temperature carbonization which, when crushed to the commercial size and on the transport disintegrates to an undesired extent to coke dross which can be utilized only with difficulty. With bituminous coal, further, the withdrawal of the finished coke cake from the coking chamber frequently is diiiicult, because in many cases, in the medium temperature carbonization, the coke does not undergo a contraction sufficient for the pushing of the coke cake at the temperature at which solidification of the crude or original coal from the plastic stage to coke takes place in medium temperature coking.

In order to eliminate these difficulties it' has been attempted to neutralize the binder existing in excess in the coal, by an addition of a nonfusible substance which so to say soaks and thus absorbs the binder in excess in the crude or original coal. As such non-fusible substance, material has been employed for example a natural non-caking coal, or a coal that has been deprived of its caking capacity by oxidation, or a coal the volatile constituents of which have been extracted in part at low temperatures by a distillation treatment (in general called semi-coke).

Furthermore, dull coal, also termed Durain, or Durite has been used as addition, or a coal enriched by dull coal, the addition rich in dull coal being obtained by a suitable treatment of crude or original coal. It is, however, not possible in all cases to obtain a concentrated mate- This is the case in particular with coals which include the dull coal in a very finely distributed condition throughoutthe coal pieces or closely grown together with coal particles of different character in the coal pieces, so that in the disintegration that must precede the treatment proper the dull coal and peacock coal, also termed Vitrain, or Vitrite, or bright coal are not separated from one another.

Now the object of my present invention is a method by which a solid coke is also produced by means of additional material for mediumtemperature carbonization from kinds of coal which include the dull coal in very finely distributed condition as aforesaid so that it cannot be separated therefrom by mechanical treatment, without whichit would be necessary to subject the coal to a heat treatment for the production of semi-coke, or to an oxidation in order to destroy its caking capacity, operations that necessitate special appliances and thus cannot be employed in all cases.

I have found that a coal rich in peacock coal and poor in dull coal, but the peacock coal being closely grown together with the dull coal, can be converted to a solid large coke, if from the predisintegrated crude or original coal the pieces of a grain size of about more than 5 mm., the dull, or Durain, or Durite constituents of the original coal, and the finest particles of a grain size of about less than 0.3 mm., the Fusain, or Fusite, or mother-of-coal constituents of the original coal, are separated and if only such a quantity of the separated particles is employed as the additional material and added to the excess binder containing coal to be coked, that the binder in excess contained in the latter coal is absorbed in the coking operation by the contact with and the binding of, this additional matter.

The finest particles, that is those of -0.3 mm., chiefly consist in so-called fibrous or Fusain, or Fusite, or mother-of-coal, constituents of the original coal, while the coarser grains of more than mm. in size in general contain plenty dull coal, or Durain, or Durite, constituents of the original coal. These two kinds of coal constituents do not cake and thus can be considered as non-fusible constituents coming within the scope of this application.

The finest particles, that means, of a grain size up to about 0.3 mm., preferably are separated from the crude or original coal by an air sifting operation, whilst the coarser grains, that is, those of more than 5 mm., which likewise form a high grade addition, easily can be separated by a usual sieving operation. The particles between 0.3 mm. and 5 mm. are what are known in the trade as Vitrain or Vitrite, or bright coal, or peacock coal constituents of the original coal.

As a matter of course, it cannot be determined 5 in general, how muchfine and coarse particles must be added to the original coal to be coked containing its natural content of both fine and coarse constituents, in order to obtain a solid large coke at the coking temperatures of the medium temperature carbonization. Bituminous coal containing about 35-38% volatile constituents, as they are being mined for example in the northern France, require about 20-30% of an addition of the finest and coarse particles.

For other kinds of coal the quantity of addition required for the medium temperature carbonization easily can be determined by a usual coking test. The addition is intimately mixed with the crude or original coal previous to the coking operation. The crude or original coal and the addition preferably are used in dry state.

For the conversion to coke of the mixture of crude coal and addition preferably chamber ovens with comparatively narrow chambers are used. If a horizontal chamber oven, as usual in normal coking plants, is made use of for the medium temperature carbonization, the width of the chamber suitably amounts to not more than 350 mm., preferably to about 280 mm. Apart from that, horizontal chamber ovens need not be adapted in any respect to the medium temperature carbonization.

While the method herein described is advantageously adapted to fulfill the object primarily stated, it is to be understood that it is not intended to confine the invention to the one form of method herein disclosed, as it is susceptible of being carried through in various forms all coming within the scope of the claim which follows.

In a process for producing a reactive, solid large medium temperature coke containing relatively high quantities of volatile matter, from coal particles having greater quantities of peacock coal constituents than required to bind its dull coal constituents on coking and having the dull coal constituents in very finely distributed condition throughout the original coal particles and closely grown together with the peacock coal constituents, the steps comprising, disintegrating the coal containing the closely grown dull coal constituents and peacock coal constituents, separately treating a portion of the disintegrated coal to separate the coarse particles of a grain size of about 5 mm. and up comprising the dull coal constituents and the fine particles of a grain size of about 0.3 mm. and less comprising the mother-of-coal constituents, mixing the aforesaid separated constituents of the treated portion with the remaining untreated disintegrated coal, said separated constituents being in the mixture in such amount relative to the untreated portion of the mixture as is required on coking to take up the excess binder of the untreated portion of the mixture, subjecting the mixture to carbonization at temperature between 600 and 750 centigrade, in a coking chamber, and removing the coke from the coking chamber as soon as vaporizable hydrocarbons no longer escape from the coking charge.

HANS AUGUST KOPPERS. 

